NO. 9 MARINE INVERTEBRATES, ALASKA — MacGINITIE 53 



to present the entire picture of the breeding habits and breeding sea- 

 sons of these Arctic invertebrates. 



METHODS OF COLLECTING AND PRESERVING 

 SPECIMENS 



DREDGING, SUMMER, 1948 AND 1949 



Since the beach and subbeach region at Point Barrow is of gravel 

 and there are no rocks for the attachment of animals, and as the 

 ocean freezes over and ice grounds out to a depth of 90 to 100 feet, 

 there is no such thing as tidal fauna, so conspicuous in many beach 

 areas. The majority of invertebrate animal life along shore occurs 

 100 feet or more beneath the surface of the water. Dredging had to 

 be employed almost exclusively for exploring the bottom, although 

 a certain amount of trapping was done through the ice (see "Trapping 

 Through the Ice"), and some grab sampling was undertaken. 



Even in summer, dredging at Point Barrow is not so simple as in 

 many regions. There is no harbor and no pier or dock, and it is not 

 possible to leave the boat anchored offshore. Consequently, each time 

 the boat was used it was necessary to push it into the water and pull 

 it ashore again. This was done with a caterpillar tractor lent by the 

 Arctic Contractors. The dates on which dredging activities began 

 and ceased were dependent on the time the ice went out in the sum- 

 mer and the time the gravel of the beach froze, for after the gravel 

 was solidly frozen the boat could not be hauled ashore without injur- 

 ing the bottom. Dredging was therefore usually limited to a period 

 beginning not earlier than the last week in July and ending early in 

 October. Hand dredging from a skiff may be possible in the second 

 or third week of July. More of the problems of dredging in the Arctic 

 are mentioned under "Currents." 



A large waterproof canvas was placed on the lo-by- 14-foot work- 

 ing space on deck and the contents of the dredge were emptied onto 

 it (pi. 3, fig. 2; pi. 4, fig. i). The material was given a preliminary 

 sorting in order to rescue the more delicate and perishable animals, 

 which were placed in jars or pails of ocean water. During October 

 1949, many of the dredged animals froze on the deck before they 

 could be taken to the laboratory. 



DREDGING, WINTER, 1949-50 



The Danes devised a method (see Thorson, 1946a) of dredging 

 through the ice by lowering a dredge to the bottom before freeze-up. 



